A prospective, randomized controlled study, using stable isotope methodology, is proposed to determine whether an oral nutrition support regimen, containing pressurized whey protein and glucose, is more effective at normalizing the metabolic response to surgery than a standard peripheral parenteral nutrition (PPN) support regimen, containing amino acids and glucose, in colorectal surgical patients studied before and after surgery. The effectiveness of the nutrition support regimens will be determined by: whole body protein balance, synthesis rates of hepatic secretory proteins, resting energy expenditure and substrate utilization, as well as circulating metabolites concentrations.